New Machine Build- Z axis

[dhaddox]

I have an old 4x8 tracer oxy/acet burn machine that I am going to take out the tracing eye and replace with a router. I am going to leave the arm that sticks out off the side on there and use it as a cnc plasma cutter. The machine already has motors and rack gears but I am going to have to upgrade the motors. I am also going to have to make a z axis and was wondering how much travel the z axis should have? Also i am not sure about motor sizing on the x axis, I plan on using servos (1 each side) with about a 10:1 reduction. The axis moves easily but is pretty heavily built (about 750 lbs) , i would like to have around 500 ipm rapds. I am not sure what size motors it would require, any input would be appreciated. Thanks

[ger21]

Originally Posted by dhaddox I am also going to have to make a z axis and was wondering how much travel the z axis should have?

Figure out where the spindle needs to be when the shortest bit you'll use reaches the table. Go a small amount lower, and that's the bottom of the travel. Then, figure out how high it has to go so that your longest tool will clear the thickest workpiece that you'll be cutting. Add a little and that's the top of your travel.

[jsheerin]

From my calculations, if you get motors that have around 3N*m of torque at 11krpm (assuming a 1" pitch diameter pinion), that would give you acceleration in the 50in/s^2 range and around 180lbf to cut with. I'm not real familiar with servos though, so I'm not sure if you can find one that turns that fast. If you didn't gear them that much, you'd need more torque but at lower rpm.